The present invention relates to methods and apparatus for detecting and preventing undesirable scale deposition, and more particularly relates, in one embodiment, to methods and apparatus for detecting and preventing undesirable scale deposition that employ electrodes which intentionally cause scale deposition as a diagnostic indicator.
The accumulation of inorganic mineral scales in oil field formation and production equipment is a major problem for the oil industry. Deposition of inorganic mineral scale in oil-bearing formations and on production tubing and equipment causes significant and costly loss of production. Other industries have similar problems with scale deposition. The primary offenders are carbonates and sulfates of calcium, barium and strontium. These compounds may precipitate as a result of changes in pressure, temperature and ionic strength of produced fluids or when connate reservoir waters mix with injected waters during secondary recovery operations. In order to avoid costly losses in production or post-scale treatments, it is necessary to prevent deposition of scale downhole as well as in post production processing. Scale is a particular problem when equipment is in contact with certain brines.
Current scale probes indicate the onset of scale deposition. However, in order to take preventive action, an advance sensor is required which detects the onset of scaling conditions before actual scale deposition occurs on the surfaces to be protected. The advantage of such a sensor would be that time for preventive measures is gained and the need for remedial work is avoided. It would be advantageous if a scale prediction probe could be devised which would be able to determine conditions just prior to when undesirable scaling would occur.
Accordingly, it is an object of the present invention to provide a method and apparatus for preventing scale from forming on surfaces, particularly oil field production equipment.
It is another object of the present invention to provide a scale prediction probe which would be able to determine conditions just prior to those under which undesirable scaling would occur.
In carrying out these and other objects of the invention, there is provided, in one form, a method for predicting scale deposition in a general environment which involves providing a localized environment where scale is preferentially formed first (relative to the general environment), where the localized environment is adjacent the general environment, and monitoring the deposition of scale in the localized environment. Preemptive action may thus be taken to prevent scale deposition in the general environment in response to the results obtained from monitoring the deposition of scale. Finally, the intentionally formed scale is removed from the localized environment so the method can be practiced again.